This invention relates to an adhesive foam composition which is safely stored, easily deployed, but very difficult to remove and thus, useful in access denial situations. The invention also relates to the foam system employed for generating the foam, and to the method of generating such a foam composition for denying access in access denial situations.
One prior art method of generating an adhesive foam is discussed in U.S. Pat. No. 4,202,279 wherein a sticky foam is generated from a tacky polymeric resin and a low boiling solvent. Typically, a thermoplastic resin comprising a blend of styrene/butadiene copolymer and polyindene, a styrene-isoprene thermoplastic elastomer, a polyterpene, an elastomeric resin, and a polyisobutylene resin is employed. The low boiling solvent serves to dissolve the resin and to provide a gas for blowing the foam. Furthermore, a nucleating agent is employed to promote the formation of fine celled foam. The foam is generated by preblending the resin and additives, and placing it in a pressurized container, and the foam is generated upon opening or rupturing of the container and releasing the contents to atmospheric pressure.
It is also known from the prior art that silicone is difficult to remove and resistant to breakdown and/or removal with common solvents and thus, it is desirable to employ a silicone based system in a use or access denial situation. However, prior silicone systems are not stable, generally require a catalyst and typically set to a rigid foam material.
U.S. Pat. No. 4,229,548 to Sattletger, et al. discloses such an organopolysiloxane foam employed as a molding or joint sealer. In a preferred formulation, polydimethylsiloxane is employed packaged under pressure with a cross-linking agent whereby when mixed and discharged, a molding composition is produced. It is noted, as discussed above, that this system is not stable over a wide temperature range, and in addition, requires a catalyst.
Other known foams of this type generally provide that the mixing of the components has to occur just prior to use. Thus, it is typically very complicated to generate such silicone adhesive foams.